Code review is a software development technique that reduces defects consistently, helping developers understand why their program works and why it fails. It involves explaining code to others, either through comments or design documents, to ensure the code is understandable and maintainable. Code reviews can be effective even when done internally, as they help identify potential issues and improve overall quality. To get the most out of a code review, reviewers should focus on understanding the code's functionality and logic, rather than just checking style or performance. Authors can prepare their code for review by providing clear comments and explanations, making it easier for others to understand and maintain. Effective code reviews involve both reviewing others' code and explaining one's own code to others, using comments and design documents to convey meaning and context. By following these principles, developers can create software that is better understood, maintained, and debugged.